The present invention relates to an intraocular lens structure designed to be seated partly in the anterior and partly in the posterior chamber of the eye after the removal of a natural lens as a result of a cataract condition.
It has been found that the insertion of an intraocular lens is by far the best solution to correcting vision after cataract surgery. The proper placement of an intraocular lens always involves the risk of damage to the eye during the insertion process as well as at a later time period if the intraocular lens dislocates or must be removed and/or replaced.
Lenses are known which permit posterior chamber fixation. At least one design of the Shearing lens employs a pair of resilient legs attached to the lens. One resilient leg of the Shearing lens is placed through a chemically dilated pupil to the area of the ciliary sulcus. The second resilient leg is coiled and forced through the pupil with the lens to the posterior chamber. The second resilient leg is released and springs back behind the iris toward the ciliary sulcus at a position therein opposite to that of the first resilient leg. The Shearing lens is preferably used only with extra capsular surgery since additional support, by the remaining posterior wall of the capsule, is available if good fixation at the ciliary sulcus is not achieved. In addition, care must be exercised during insertion of the Shearing lens since otherwise there may result severence of the zonules which would allow the Shearing lens to travel into the vitreous humor behind the iris. While maximum pupil size is desirable to facilitate proper fixation of these known posterior chamber lenses, adequate dilation of the pupil is not possible in every case. Moreover, the releasing of the second resilient leg of a Shearing lens creates a whip-like action which can tear the iris, or the ciliary body, or the posterior capsule, resulting in bleeding and loss of capsular support. Moreover, forcefully retracting the iris with a forceps to allow the second resilient leg to pass behind it can also cause damage to the iris. All in all, suitable posterior fixation of the Shearing lenses is difficult to predict and visualization of the fixation is totally impossible since the ciliary sulcus is totally hidden by the iris and is, therefore, invisible to the surgeon. Furthermore, removal of such a lens, should such be indicated at some later date, is extremely difficult and sometimes dangerous.
There is a need for a lens which may be easily fixed into the posterior chamber of the eye, which offers a superior means of support without substantial damage to the eye during and after implantation, and which will facilitate removal of the lens at a later date should such removal be indicated.